TW202248346A - Polyester resin composition, aqueous dispersion, coating composition, and coating film - Google Patents

Abstract

To provide a polyester resin and a polyester resin composition which are capable of suppressing toxic outgassing, while being capable of forming a coating film that exhibits excellent characteristics such as excellent curability, retort resistance and processability. A polyester resin composition which contains a polyester resin (A) that has an acid value of not less than 100 eq/ton but less than 500 eq/ton and a polyester resin (B) that has an acid value of not less than 500 eq/ton, wherein: if the total mass of the solid contents of the polyester resin (A) and the polyester resin (B) is taken as 100 parts by mass, the polyester resin (A) is within the range of from 55 parts by mass to 95 parts by mass, and the polyester resin (B) is within the range of from 5 parts by mass to 45 parts by mass.

Description

Polyester resin composition, aqueous dispersion, coating composition and coating film

This invention relates to polyester resin compositions. More specifically, it relates to a polyester resin composition suitable for can coatings, and more specifically, it relates to a polyester resin composition suitable for coating the inside of cans containing beverages and food (hereinafter collectively referred to as food and beverages). An ester resin composition, an aqueous dispersion containing the composition, a coating composition, a coating film, and a metal can having the coating film.

Metal cans such as beverage cans and food cans are coated with organic resins in order to prevent corrosion of the metal caused by food (corrosion resistance) and not to damage the taste and flavor of the contents (taste). Such coating requires workability, corrosion resistance, adhesion to metal materials, hardening properties, and the like. Also, depending on the application, coating may be performed under high temperature and high humidity conditions such as cooking and sterilization. In this case, not only the coating film must maintain the adhesion to the metal material, but it is also required to be used especially for metal covers. Whitening of the coating film does not occur when waiting for the outer side.

Conventionally, epoxy-phenolic paints, epoxy-amine paints, epoxy-acrylic paints, and other epoxy-based paints, polymer paints, etc. Polyester-based coatings such as ester-phenol-based coatings, polyester-amine-based coatings, and vinyl chloride-based coatings. However, recent studies have reported that bisphenol A, which is a raw material for epoxy resins, may affect estrogen, the brains of fetuses, and infants. In addition, vinyl chloride-based paints have the problem of stabilizers and the generation of dioxins during incineration. It is known that formaldehyde, which is used as a raw material for phenolic resins, amino resins, etc. and remains in paints, is harmful to the human body, such as carcinogenicity, and also adversely affects the taste of the contents. In addition, there will be concerns about the environmental pollution caused by the use of organic solvents and the impact on the working environment.

Considering such concerns about various adverse effects on the human body, water-based paints that do not use these raw materials are desired on the market, but it is true that satisfactory performance cannot be obtained for can use.

Considering such a point of view, as a resin composition for metal containers or metal lids, for example, a water-based coating composition has been proposed, which is to graft-polymerize a polymerizable unsaturated monomer component to a polymer having an ethylenic double bond at the end of the resin. An acrylic-modified polyester resin made of an ester resin and a β-hydroxyalkylamide crosslinking agent are dispersed in an aqueous medium (Patent Document 1).

Also, Patent Document 2 proposes a coating composition composed of polyester polyol and a blocked polyisocyanate hardener. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-81160 [Patent Document 2] Japanese Unexamined Patent Publication No. 2006-169535

[Problem to be Solved by the Invention]

However, when the high-acid-value acrylic-modified polyester resin described in Patent Document 1 is used, sufficient processability cannot be obtained. In addition, unreacted substances of the β-hydroxyalkylamide crosslinking agent remain in the coating film, and there is a problem that curability and retort whitening properties are lowered. The coating film obtained by reacting polyester and blocked polyisocyanate described in Patent Document 2 has the problem of poor water resistance and whitening of the content when the content is sterilized.

The object of the present invention is to provide a polyester resin composition. By curing the polyester resin without substantially containing a curing agent, harmful outgassing can be suppressed, and hardening, retort resistance, and processability can be formed. Coating films with excellent properties. [Means to solve the problem]

The inventors of the present invention conducted various studies on the above-mentioned matters, and found that a polyester resin composition obtained by combining polyester resins having a specific amount of acid value can be used only by heat treatment without substantially using a curing agent. It hardens. In addition, the inventors of the present invention found that by specifying the resin composition of the polyester resin and controlling the amount of the catalyst, a polyester with an excellent balance between hardenability and processability, no harmful outgassing, and significantly improved retort resistance can be obtained. Resin coating film, and completed the present invention. That is, the present invention has the following configurations.

[1] A polyester resin composition comprising a polyester resin (A) having an acid value of 100 eq/ton or more and less than 500 eq/ton, and a polyester resin (B) having an acid value of 500 eq/ton or more, wherein the poly When the total solid content mass of the ester resin (A) and the polyester resin (B) is 100 parts by mass, the polyester resin (A) is in the range of 55 parts by mass to 95 parts by mass, and the polyester resin (B) is 5 parts by mass. The range of not less than 45 parts by mass and not more than 45 parts by mass. [2] The polyester resin composition according to the aforementioned [1], which substantially does not contain a curing agent. [3] The polyester resin composition according to [1] or [2] above, wherein the polyester resin (A) contains a diol (a) having two primary hydroxyl groups and no alicyclic structure, and further contains Either or both of the diol (b) of the alicyclic structure and the diol (c) having one primary hydroxyl group and one secondary hydroxyl group and not having an alicyclic structure, as the constituents of the aforementioned polyester resin ( A) The polyol component. [4] The polyester resin composition according to the aforementioned [1] to [3], wherein both the polyester resin (A) and the polyester resin (B) have a branched structure. [5] The polyester resin composition according to [1] to [4] above, wherein the polyester resin (A) contains an unsaturated dicarboxylic acid (d) as a polyvalent carboxylic acid component constituting the polyester resin (A) . [6] The polyester resin composition as described in [1] to [5] above, wherein the tetrahydrofuran insoluble matter after heat treatment at 150°C for 30 minutes is less than 10% by mass, and further contains one or more catalysts (C) . [7] The polyester resin composition according to the aforementioned [6], wherein the content of the catalyst (C) is 0.01 to 0.5 parts by mass based on 100 parts by mass of the total amount of the polyester resin (A) and the polyester resin (B). parts by mass. [8] An aqueous polyester resin dispersion comprising the polyester resin composition as described in [1] to [7] above, and an aqueous medium. [9] A paint composition comprising the polyester resin composition of the aforementioned [1] to [7] or the polyester resin aqueous dispersion of the aforementioned [8]. [10] A coating film comprising the polyester resin composition of the above-mentioned [1] to [7]. [11] A metal can having the coating film according to the aforementioned [10]. [Effect of Invention]

The present invention can provide a polyester resin composition and a coating film thereof that do not generate harmful outgassing from a curing agent, have an excellent balance between curability and workability, and have remarkably improved retort resistance.

Hereinafter, embodiments of the present invention will be described in detail.

＜Polyester resin (A)＞ The acid value of the polyester resin (A) used in the present invention must be above 100eq/ton. It is preferably at least 200 eq/ton, more preferably at least 250 eq/ton, and most preferably at least 300 eq/ton. If it is less than the above-mentioned value, since there are few carboxyl groups serving as crosslinking points, the curability may decrease. In addition, when the acid value is less than the above value, when heated to 240° C., the thermal decomposition reaction proceeds prior to the hardening reaction, and the workability may decrease. Moreover, aqueous dispersion becomes easy when an acid value is more than the said lower limit. In order to reduce the amount of unreacted substances and oligomers of the acid component during the acid addition reaction, the upper limit of the acid value is less than 500eq/ton. It should be below 400eq/ton.

The acid value of a polyester resin (A) can be provided by arbitrary methods. As for the method of imparting acid value, there is a method of adding polycarboxylic acid anhydride in the late stage of polycondensation, making it high in acid value at the stage of prepolymer (oligomer), and then polycondensing it As for the method for obtaining a polyester resin having an acid value, the former method of performing an addition reaction is preferable in consideration of the ease of operation and the ease of obtaining the target acid value.

Among the compounds having polycarboxylic acid anhydride groups in the molecule for imparting acid value to the polyester resin (A), examples of carboxylic acid monoanhydrides include phthalic anhydride, succinic anhydride, maleic anhydride, meta Monoanhydrides such as benzenetricarboxylic anhydride, itaconic anhydride, citraconic anhydride, 5-(2,5-dipentoxytetrahydrofurfuryl)-3-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride Diformic anhydride, tetrahydrophthalic anhydride, and the like can be used by selecting one or more of these. Among them, trimellitic anhydride is preferable in consideration of versatility and economy.

Among the compounds having polycarboxylic acid anhydride groups in the molecule for imparting an acid value to the polyester resin (A), examples of carboxylic acid polyanhydrides include: pyromelite anhydride, 1,2,3,4-butane Tetracarboxylic dianhydride, 1,2,3,4-pentane tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ketone tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride , 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, ethylene glycol bis-trimellitic acid dianhydride, 2,2',3, 3'-diphenyltetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 5 -(2,5-Dioxotetrahydro-3-furan)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, etc., one or more kinds can be selected from these use. Among them, ethylene glycol bis-trimellitic acid dianhydride is preferable.

As the compound having polycarboxylic acid anhydride groups in the molecule for imparting the aforementioned acid value, carboxylic acid monoanhydrides and carboxylic acid polyanhydrides may be used alone or alternatively.

The polyester resin (A) is composed of a polyvalent carboxylic acid component and a polyhydric alcohol component. As the polyol component constituting the polyester resin (A), it is preferable to contain a diol (a) having two primary hydroxyl groups and not having an alicyclic structure (hereinafter, may be referred to as (a) component). The diol (a) which has two primary hydroxyl groups and does not have an alicyclic structure in a polyester resin (A), For example, ethylene glycol, 1, 3-propanediol, 2-butyl-2-ethyl -1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,4-butanediol, 2,4-diethylene 1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl-1 , 7-heptanediol, 4-methyl-1,8-octanediol, 1,9-nonanediol and other aliphatic diols; diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol , polyether glycols such as polytetramethylene glycol, and the like, and one or more of them may be selected and used. Among them, ethylene glycol, 2-methyl-1,3-propanediol, and 1,6-hexanediol are preferably used.

The copolymerization ratio of the diol (a) having two primary hydroxyl groups and no alicyclic structure in the polyester resin (A) is preferably 20-80 mole % of all polyol components, more preferably 20 ～60 mol%, preferably 20～40 mol%. When it exists in the said range, curability and retort resistance will become favorable.

The polyester resin (A) preferably contains a diol (b) having an alicyclic structure as a polyol component. By containing the diol (b) (it may be called (b) component hereinafter) which has an alicyclic structure, it becomes easy to make processability and retort resistance compatible. Diols (b) having an alicyclic structure constituting the polyester resin (A) include, for example, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexane Dimethanol, tricyclodecanediols, hydrogenated bisphenols, and the like can be used by selecting one or more of them. Among them, 1,4-cyclohexanedimethanol is preferably used from the viewpoint of hardenability, workability, and retort resistance.

The copolymerization ratio of the diol (b) having an alicyclic structure constituting the polyester resin (A) is preferably 5-50 mol%, more preferably 10-40 mol%, of the total polyol components, especially It is 20-30 mole%. When it exists in the said range, processability will become favorable.

The polyester resin (A) preferably contains, as a polyol component, a diol (c) having one primary hydroxyl group and one secondary hydroxyl group and not having an alicyclic structure (hereinafter, may be referred to as component (c)). The diol (c) which has one primary hydroxyl group and one secondary hydroxyl group and does not have an alicyclic structure in the polyester resin (A) includes, for example, 1,2-propanediol, 1,2-butanediol, etc. , and one or more of these can be selected for use. Among them, 1,2-propanediol is preferably used.

The copolymerization ratio of the diol (c) having one primary hydroxyl group and one secondary hydroxyl group and not having an alicyclic structure in the polyester resin (A) is preferably 5 to 75 moles in all polyol components %, more preferably 10-65 mol%, especially 15-50 mol%. When it exists in the said range, curability and retort resistance will become favorable.

The polyester resin (A) preferably contains either or both of the above-mentioned (a) component, (b) component, and (c) component. Presumably, since the (a) component is easy to form an ester bond, on the other hand, the (b) component and (c) component, the ester bond is easier to crack than the (a) component, so by having (a) component, and (b) ) component or (c) component, the rearrangement and rebonding of ester bonds will be promoted during heat treatment, the THF insoluble matter will increase, and a coating film with both hardenability and flexibility, that is, processability, can be formed.

Examples of the polyvalent carboxylic acid component constituting the polyester resin (A) include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, Aromatic dicarboxylic acid components such as 1,8-naphthalene dicarboxylic acid, etc. These can be used alone or in combination of two or more. Among them, terephthalic acid and 2,6-naphthalene dicarboxylic acid are preferable.

Examples of other polyvalent carboxylic acid components constituting the polyester resin (A) include aliphatic dicarboxylic acid components and alicyclic dicarboxylic acid components. Examples of the aliphatic dicarboxylic acid component include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid. Examples of the alicyclic dicarboxylic acid component include 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalic acid, and 1,2-cyclohexenedicarboxylic acid. One or more of these can be selected and used. Among them, adipic acid and 1,4-cyclohexanedicarboxylic acid are preferable in terms of reactivity and economy.

When the polyester resin (A) has an aliphatic dicarboxylic acid component and an alicyclic dicarboxylic acid component as constituent units, their copolymerization ratio is preferably 5 to 40 mol% in the polyvalent carboxylic acid component. More preferably, it is 10 to 30 mol%. If it falls outside the said range, the glass transition temperature of a polyester resin (A) will fall significantly, and retort resistance may fall.

It is also preferable to contain unsaturated dicarboxylic acid (d) as a structural unit as a polyhydric carboxylic acid component which comprises a polyester resin (A). By containing the unsaturated dicarboxylic acid (d), curability can be improved by utilizing the reaction of forming intermolecular carbon-carbon bonds due to the cleavage of unsaturated bonds during heat treatment. Examples of the aforementioned unsaturated dicarboxylic acid (d) include fumaric acid, maleic acid, itaconic acid, citraconic acid, 2,5-norbornanedicarboxylic acid, and tetrahydrophthalic acid. , and their anhydrides, one or two or more of these can be used.

When the polyester resin (A) contains unsaturated dicarboxylic acid (d) as a constituent unit, the copolymerization ratio of unsaturated dicarboxylic acid (d) is preferably 5 to 20 mol% in the polycarboxylic acid component. More preferably, it is 10-15 mol%. By being within the above range, both workability and hardenability can be achieved.

The polyester resin (A) preferably has a branched structure. Having a branched structure means that the main chain of the polyester has a branched structure. For the introduction of a branched structure into the polyester resin (A), as an example, in the polycondensation reaction of polyester, a component with more than three functions A method of copolymerizing as part of the polycarboxylic acid component and/or the polyol component. Examples of trifunctional or higher polycarboxylic acid components include: trimellitic acid, pyromeltaric acid, benzophenone tetracarboxylic acid, etc. Examples of trifunctional or higher polyhydric alcohols include glycerin, trimethylol Ethane, trimethylolpropane, mannitol, sorbitol, neoerythritol, α-methyl glucoside, etc. Since the polyester resin (A) has a branched structure, the rearrangement of ester bonds during heat treatment and the increase in crosslink density when rebonding occurs will increase THF insoluble matter and improve hardenability and processability.

The copolymerization ratio of polycarboxylic acid components with more than 3 functionalities is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, and most preferably 1 mol% or more when the total polycarboxylic acid components are 100 mol%. . Moreover, it is preferably not more than 7 mol%, more preferably not more than 6 mol%, especially preferably not more than 5 mol%, and most preferably not more than 4 mol%. The copolymerization ratio of the polyol component having 3 or more functions is preferably at least 0.1 mol%, more preferably at least 0.5 mol%, and most preferably at least 1 mol% when the total polyol component is 100 mol%. Moreover, it is preferably not more than 5 mol%, more preferably not more than 3 mol%, especially preferably not more than 2 mol%, and most preferably not more than 1 mol%. When the polycarboxylic acid component and the polyol component exceed the above-mentioned values, the flexibility of the polyester resin may be lost, the processability may be lowered, or the polyester may be gelled during polymerization.

The manufacturing method of polyester resin (A) is demonstrated. In the esterification/exchange reaction, all monomer components and/or low polymers thereof are heated and melted to react. The esterification/exchange reaction temperature is preferably 180-250°C, more preferably 200-250°C. The reaction time is preferably 1.5-10 hours, more preferably 3-6 hours. Furthermore, the reaction time is defined as the time from reaching the desired reaction temperature until the subsequent polycondensation reaction. In the polycondensation reaction, under reduced pressure and at a temperature of 220-280°C, the polyol component is distilled off from the esterified product obtained in the esterification reaction, and the polycondensation reaction is continued until the desired molecular weight is reached. The reaction temperature of polycondensation is preferably 220-280°C, more preferably 240-275°C. The degree of reduced pressure should be below 130Pa. If the decompression degree is insufficient, the condensation polymerization time tends to be long, which is not preferable. The decompression time from atmospheric pressure to below 130Pa should be decompressed slowly for 30 to 180 minutes.

In the case of esterification/exchange reaction and polycondensation reaction, if necessary, organic titanate compounds such as tetrabutyl titanate, germanium dioxide, antimony oxide, tin octoate and other organic tin compounds can be used for polymerization. In consideration of reactivity, organic titanate compound is preferred, and in consideration of resin coloring, germanium dioxide is preferred.

The glass transition temperature of the polyester resin (A) is preferably 40°C or higher, more preferably 60°C or higher, in consideration of water resistance, especially retort resistance of the coating film. The upper limit of the glass transition temperature is not particularly limited, but is usually 130°C or lower.

The reduced viscosity of the polyester resin (A) is preferably 0.2-0.6 dl/g, more preferably 0.3-0.5 dl/g. If the reduced viscosity is less than 0.2 dl/g, the hardenability becomes insufficient, and the toughness of the coating film is insufficient, and after coating on a metal plate, it may not be able to withstand the molding process of making a can. On the other hand, if the reduced viscosity exceeds 0.6 dl/g, the melt viscosity and solution viscosity will increase, and not only the workability will be reduced, but also the acid value may not be sufficiently imparted due to the decrease in the number of terminal hydroxyl groups.

＜Polyester resin (B)＞ The acid value of the polyester resin (B) used in the present invention is 500 eq/ton or more. More preferably, it is more than 600 eq/ton, and most preferably, it is more than 800 eq/ton. By using the polyester resin (B) having an acid value of the aforementioned value, the effect of curing the polyester resin composition in a short time can be obtained. If the acid value is lower than the above-mentioned value, it is difficult to carry out the crosslinking reaction in a short time, and it is difficult to obtain the effect obtained by blending the polyester resin (B) into the polyester resin composition.

The method of imparting an acid value to the polyester resin (B) can be carried out by the same method as the above-mentioned polyester resin (A). A preferred method and a compound having a polyvalent carboxylic acid anhydride group that can be preferably used for imparting an acid value are also the same as the polyester resin (A).

As the polyhydric alcohol component and the polyvalent carboxylic acid component constituting the polyester resin (B), the same constituent components as those of the above-mentioned polyester resin (A) can be used. Desirable constituents and content are also the same as those of the polyester resin (A). The production method can also be produced in the same manner as the method for producing the polyester resin (A).

The polyester resin (B) preferably has a branched structure. The method of introducing the branched structure can be carried out by the same method as the aforementioned polyester resin (A).

The glass transition temperature of the polyester resin (B) is preferably 40°C or higher, more preferably 60°C or higher, in consideration of water resistance, especially retort resistance of the coating film. The upper limit of the glass transition temperature is not particularly limited, but is usually 130°C or lower.

The reduced viscosity of the polyester resin (B) is preferably 0.1-0.3 dl/g, more preferably 0.15-0.2 dl/g. If the reduced viscosity is less than 0.1dl/g, the workability will be insufficient, the strength and toughness of the coating film will be insufficient, and after coating on a metal plate, it may not be able to withstand the forming process of making a can. On the other hand, if the reduced viscosity exceeds 0.3 dl/g, the melt viscosity and solution viscosity will increase, and not only the workability will be reduced, but also the acid value may not be sufficiently imparted due to the decrease in the number of terminal hydroxyl groups.

In the present invention, the polycarboxylic acid component and the polyhydric alcohol component constituting the polyester resin (A) and the polyester resin (B) can use raw materials derived from biomass resources. Biomass resources refer to those that use the photosynthesis of plants to convert the sun's light energy into starch, cellulose and other forms of storage, animal bodies that grow by eating plants, and products obtained by processing plants and animal bodies. Among them, more preferable biomass resources are plant resources, such as wood, straw, rice husk, rice bran, aged rice, corn, sugarcane, cassava, sago, bean dregs, corncobs, cassava bagasse, bagasse, vegetable oil Slag, tuber root, buckwheat, soybean, oil, waste paper, papermaking residue, aquatic product residue, livestock excrement, sewage sludge, food waste, etc. Especially preferred are corn, sugarcane, cassava, and sago.

＜Polyester resin composition＞ In the polyester resin composition of the present invention, when the total solid content mass of the polyester resin (A) and the polyester resin (B) is 100 parts by mass, the polyester resin (A) is 55 parts by mass or more and 95 parts by mass The range below the number of copies. It is preferably 60 to 90 parts by mass, more preferably 70 to 85 parts by mass. The polyester resin (B) is not less than 5 parts by mass and not more than 45 parts by mass. It is preferably 7 to 40 parts by mass, more preferably within a range of 10 to 30 parts by mass. When the polyester resin (A) is more than this range and the polyester resin (B) is less than this range, there may be a large amount of uncrosslinked polyester resin inside the coating film, and the curability of the entire coating film may be insufficient. On the other hand, when the polyester resin (A) is less than this range and the polyester resin (B) is more than this range, the thermal decomposition reaction is likely to be promoted, and sufficient curability may not be obtained.

In the polyester resin composition of the present invention, the polyester resin composition can be cured in a short period of time by heat treatment even if no curing agent is blended using the polyester resin (B) as described above. Therefore, the polyester resin composition of the present invention preferably does not contain a hardener substantially. The "substantially not containing a curing agent" means "the content of the curing agent is less than 1 mass (solid conversion) with respect to a total of 100 mass parts (solid conversion) of the polyester resin". Here, the curing agent refers to a known curing agent that reacts with the polyester resin (A) and polyester resin (B) of the present invention to form a crosslinked structure, and the form of the crosslinked structure includes, for example: Free radical addition reaction, cationic addition reaction, or anion addition reaction, etc., react unsaturated double bonds in polyester resin to generate intermolecular carbon-carbon bonds, and react with polycarboxylic acid groups in polyester resins , The formation of intermolecular bonds caused by condensation reactions of polyol groups, addition polymerization reactions, or transesterification reactions, etc. Examples of the curing agent include phenolic resins, amine resins, isocyanate compounds, epoxy compounds, β-hydroxylamide compounds, unsaturated bond-containing resins, and the like.

In the polyester resin composition of the present invention, the content of the curing agent is preferably less than 1 part by mass based on 100 parts by mass of the total solid content of the polyester resin (A) and polyester resin (B). It is more preferably less than 0.5 parts by mass, more preferably less than 0.1 parts by mass, and it is most preferably not to contain a hardener. When the content of the curing agent is more than the above range, not only the economic efficiency is poor, but also the workability is reduced due to the self-condensation reaction between the curing agents, the volatilization of the end-capping agent, the generation of harmful fugitive gases such as formaldehyde, and poor long-term storage stability risk.

The polyester resin composition of the present invention can be cured by heat treatment at 240° C. for a short time of 5 minutes even if it does not substantially contain a curing agent as described above. On the other hand, before heat treatment, it is preferable to contain no cured product as much as possible from the viewpoint of handling properties such as solvent solubility and resin aggregation. The content of such hardened matter can be known by using tetrahydrofuran (THF) insoluble matter as an index.

In the polyester resin composition of the present invention, the tetrahydrofuran insoluble matter after heat treatment at 240° C. for 5 minutes is preferably 10% by mass or more. When the tetrahydrofuran (THF) insoluble matter is 10 mass % or more, the polyester resin composition and its coating film which are excellent in the balance of retort resistance and processability can be obtained. The THF insoluble matter is preferably at least 30% by mass, more preferably at least 50% by mass, and most preferably at least 70% by mass. When it is less than 10% by mass, the curability becomes insufficient, the strength and toughness of the coating film are insufficient, the retort resistance may be reduced, and the molding process of making cans after coating on a metal plate may not be able to withstand.

On the other hand, in the polyester resin composition of the present invention, THF insoluble matter after heat treatment at 150° C. for 30 minutes is preferably less than 10% by mass. More preferably, it is less than 5% by mass, particularly preferably, it is less than 1% by mass, and it is not a problem if it is 0% by mass. Since the THF insoluble matter does not reach the above-mentioned value under heating conditions at a relatively low temperature of about 150° C., generation of aggregates when dissolved in a solvent or when made into an aqueous dispersion can be suppressed. The same goes for each of the polyester resin (A) and the polyester resin (B), and it is preferable that the THF insoluble matter after heat treatment at 150° C. for 30 minutes does not reach the above-mentioned value.

＜Catalyst (C)＞ The polyester resin composition of the present invention preferably further contains a catalyst (C). By containing the catalyst (C), the self-crosslinking properties of the polyester resin (A) and the polyester resin (B) during heat treatment can be promoted, and the curability can be improved. Examples of the catalyst include acid catalysts such as sulfuric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalene disulfonic acid, camphorsulfonic acid, and phosphoric acid. Organotin compounds such as dibutyltin dilaurate, titanium compounds such as tetrabutoxytitanium, zinc compounds such as zinc acetate, hafnium chloride, etc. For hafnium compounds such as -THF complexes and rare earth compounds such as scandium trifluoromethanesulfonate, one or more of these compounds may be used. Among them, dodecylbenzenesulfonic acid and its neutralized product are preferable in consideration of compatibility with the polyester resin (A) and the polyester resin (B) and sanitation.

The blending ratio of polyester resin (A), polyester resin (B) and catalyst (C) used in the present invention should be {(A)+(B)}/(C)=100/0.01～0.5 (parts by mass), particularly preferably 100/0.05 to 0.4 (parts by mass), most preferably 100/0.1 to 0.3 (parts by mass). By being within the above range, the curability of the polyester resin composition can be improved.

In the polyester resin composition of the present invention, the catalyst (C) may be contained in the polyester resin (A) and the polyester resin (B), or may be added thereafter. In view of avoiding gelation of the polyester resin during polymerization, the catalyst (C) is preferably added after the production of the polyester resin (A) and polyester resin (B).

In the polyester resin composition of the present invention, a radical polymerization inhibitor (D) may also be added. It is mainly used to prevent gelation caused by unsaturated bond cracking when polyester resin (A) and polyester resin (B) are polymerized, but in order to improve the storage stability of polyester resin, it can also be used in Added after aggregation. Examples of the radical polymerization inhibitor (D) include known ones such as phenolic antioxidants, phosphorus antioxidants, amine antioxidants, sulfur antioxidants, and inorganic compound antioxidants.

Examples of phenolic antioxidants include: 2,5-di-tert-butylhydroquinone, 4,4'-butylene bis(3-methyl-6-tert-butylphenol), 1,1,3 - ginseng (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-ginseng (3,5-di-tertiary Butyl-4-hydroxybenzyl)benzene, ginseng(3,5-di-tert-butyl-4-hydroxyphenyl)isocyanurate, etc., or derivatives thereof, etc.

Examples of phosphorus-based antioxidants include tris(nonylphenyl) phosphite, triphenyl phosphite, diphenylisodecyl phosphite, tris(octadecyl) phosphite, tridecyl phosphite, Diphenyldecyl phosphite, 4,4'-butylene-bis(3-methyl-6-tert-butylphenylbis(tridecyl)phosphite), distearyl-neopentyl Tetrol diphosphite, trilauryl trithiophosphite, etc., or derivatives thereof, etc.

Examples of amine-based antioxidants include: phenyl-β-naphthylamine, phenanthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine Amine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, aldol-α-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, etc., or their derivatives, etc.

Examples of sulfur-based antioxidants include: thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, tetramethylthiuram disulfide, isopropyl Nickel xanthate, etc., or their derivatives.

Examples of nitro compound-based antioxidants include: 1,3,5-trinitrobenzene, p-nitrosodiphenylamine, p-nitrosoxylidine, 1-chloro-3-nitrobenzene, o-dinitrobenzene phenylbenzene, m-dinitrobenzene, p-dinitrobenzene, p-nitrobenzoic acid, nitrobenzene, 2-nitro-5-cyanothiophene, etc., or their derivatives.

Examples of inorganic compound antioxidants include FeCl ₃ , Fe(CN) ₃ , CuCl ₂ , CoCl ₃ , Co(ClO ₄ ) ₃ , Co(NO ₃ ) ₃ , Co ₂ (SO ₄ ) ₃ and the like.

As the radical polymerization inhibitor (D) used in the present invention, among the above-mentioned antioxidants, phenolic antioxidants and amine antioxidants are preferable from the viewpoint of thermal stability, and those having a melting point of 120°C or higher and a molecular weight of 200 or higher More preferably, those having a melting point of 170° C. or higher are especially preferable. Specifically, it is phenanthrene, 4,4'-butylenebis(3-methyl-6-tert-butylphenol) and the like.

The blending ratio of the polyester resin (A) used in the present invention and the radical polymerization inhibitor (D) is preferably (A)/(D)=100/0.001～0.5 (weight parts), especially preferably 100/ 0.01 to 0.1 (parts by weight), most preferably 100/0.02 to 0.08 (parts by weight). The blending ratio of the polyester resin (B) and the radical polymerization inhibitor (D) is also the same as above, and by being within the aforementioned range, condensation during the production of the polyester resin (A) and the polyester resin (B) can be suppressed. gelled.

In the polyester resin composition of the present invention, conventional inorganic pigments such as titanium oxide and silicon dioxide, phosphoric acid and its esterified products, surface smoothing agents, defoamers, dispersants, lubricants, etc. known additives. In particular, lubricants are important for imparting lubricity to the coating film required for forming DI tanks, DR (or DRD) tanks, etc. Examples include fatty acid ester waxes, silicone waxes, Fluorine-based waxes, polyolefin waxes such as polyethylene, lanolin-based waxes, montan waxes, microcrystalline waxes, and the like are exemplified as ideal lubricants. Lubricants can be used alone or in combination of two or more.

The polyester resin composition of the present invention can be made into a paint in the state of being dissolved in a known organic solvent. The organic solvents used for coating, for example, include: toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, methyl cellosulfone, butyl Kiselosu, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, ethylene glycol monoacetate, methanol, ethanol, butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, Solvesso, etc. One or more of these may be selected and used in consideration of solubility, evaporation rate, and the like.

The polyester resin composition of the present invention can be made into a powder coating by a known pulverization method. As a known pulverization method, a pulverization method is mentioned, for example. In the pulverization method, the mixture of the polyester resin composition of the present invention, anti-rust pigments and additives, etc. if necessary, is dry-mixed with a mixer such as a drum mixer or a Henschel mixer, and mixed by a kneader. Perform melt kneading. As the kneading machine, general kneading machines such as a single-screw or twin-screw extruder, a three-roll mill, and a Labo Plastomill can be used, for example. The kneaded product is cooled and solidified, and the solidified product is roughly pulverized and finely pulverized to obtain a pulverized product. As a pulverizer, for example, a jet pulverizer that utilizes a supersonic jet stream for pulverization, and a space formed between a rotor (rotor) and a stator (liner) rotating at a high speed are introduced and Impact mill for crushing. In addition, additives may be further added to the pulverized product if necessary. The pulverized product can be classified to adjust the powder to a desired particle size and a desired particle size distribution to obtain a powder coating composition. Classification can use a conventional classifier capable of removing over-crushed toner mother particles by classification using centrifugal force and wind force, for example, a rotary wind classifier (rotary wind classifier) or the like can be used.

In the polyester resin composition of the present invention, other modified resins may be blended in order to impart flexibility, adhesiveness, etc. to the coating film. Examples of other resins include crystalline polyesters, ethylene-polymerizable unsaturated carboxylic acid copolymers, and ethylene-polymerizable carboxylic acid copolymer ionomers, and by blending at least one selected from these The above resins may impart flexibility and/or adhesiveness to the coating film.

The polyester resin composition of the present invention can be coated on one or both sides of the metal plate as long as it is made of a metal material that can be used for beverage cans, cans for cans, their lids, lid materials, etc. Can be applied to end faces. As said metal material, tinplate, tin-free steel, aluminum etc. are mentioned, for example. It can also be used in metal plates composed of these metal materials that have been pre-treated with phosphoric acid treatment, chromate chromate treatment, phosphoric acid chromate treatment, anti-corrosion treatment with other anti-rust treatment agents, in order to improve the coating film Adhesive surface treatment obtained.

The polyester resin composition of the present invention can be applied to a metal plate by a known coating method such as roll coater coating and spray coating, and then cured. The coating film thickness is not particularly limited, but the dry film thickness is preferably in the range of 3-18 μm, more preferably in the range of 5-15 μm. The baking conditions of the coating film are usually preferably in the range of about 180-260°C for about 10 minutes to 2 hours, more preferably in the range of about 200-240°C for about 5 minutes-1 hour.

＜Water dispersion of polyester resin＞ The polyester resin composition of the present invention can also be used in the form of an aqueous polyester resin dispersion dispersed in an aqueous medium. As a method of water-dispersing the polyester resin (A) and polyester resin (B) of the present invention, there is the following method: dissolving in a water-soluble In an organic solvent, the method (a) of gradually adding a basic compound and water to disperse as needed; adding polyester resin (A) and polyester resin (B), water, will dissolve polyester resin (A) and polyester The method (b) of heating and dispersing the water-soluble organic solvent of the resin (B), a basic compound if necessary, and the like. Also, when the amount of organic solvent is to be reduced, or when water dispersion is to be completely removed from the organic solvent, the solvent may be removed under heating or reduced pressure after dispersing using an organic solvent having a boiling point of 100°C or lower. In the case of the polyester resin (A) and the polyester resin (B), it is preferable to perform the former method (a) from the viewpoint of film forming properties.

At this time, the temperature when the polyester resin (A) and the polyester resin (B) are dissolved is preferably 40-160°C, more preferably 50-140°C, more preferably 60-120°C, and most preferably 70-100°C . If the temperature is lower than 40°C, the dissolution of the polyester resin (A) and the polyester resin (B) will be insufficient, so the entanglement between the molecular chains cannot be fully untied, and if the temperature exceeds 160°C, The risk of causing deterioration of the polyester resin (A) and the polyester resin (B) increases. Organic solvents capable of dissolving polyester resin (A) and polyester resin (B) by heating in a temperature range of 40 to 160°C include methyl ethyl ketone, dimethylacetamide, dimethylformamide, N -Methylpyrrolidone, Tetrahydrofuran, 1,4-Dioxane, 1,3-Dioxane, 1,3-Dioxane, 1,2-Hexanediol, Methylcelloxane, Butylcelloxane Su, ethyl carbitol, butyl carbitol, propylene glycol monopropyl ether, propylene glycol monobutyl ether, triethylene glycol monobutyl ether, etc. Among them, methyl ethyl ketone, butylcytosol, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and the like are preferable.

When dissolving polyester resin (A) and polyester resin (B) above 100°C, it is necessary to cool the temperature of the polyester resin solution to below 100°C, then add water and alkali as needed while stirring the resin solution active compound, to undergo phase inversion whereby an aqueous dispersion is obtained.

The basic compound used when water-dispersing the polyester resin (A) and polyester resin (B) of the present invention is preferably a compound that volatilizes during the drying and baking steps when the coating film is formed. Ammonia and/or organic amine compounds with a boiling point of 250°C or less are used. Ideal examples include: triethylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, aminoethanolamine, N-methyl-N,N-diethanolamine, isopropylamine, iminobis Propylamine, ethylamine, diethylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, second butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, methyliminodipropylamine, 3-Methoxypropylamine, monoethanolamine, diethanolamine, triethanolamine, thioline, N-methyl thioline, N-ethyl thioline, etc. These basic compounds need to be at least partially neutralized with the carboxyl groups of the polyester resin (A) and polyester resin (B). Specifically, it is ideal to add 0.5-1.5 equivalents relative to the carboxyl equivalents.

The average particle size of the polyester resin aqueous dispersion of the present invention will significantly affect the appearance and storage stability of the coating film, so it is very important and should be 30-250nm. Most preferably, it is 50 to 200 nm, and most preferably, it is 70 to 150 nm. When the average particle diameter exceeds 250 nm, not only the dispersion stability is greatly reduced, but also the film-forming property is also reduced, so that the appearance of the obtained film is deteriorated. On the other hand, if the thickness is less than 30 nm, the film forming property tends to be significantly improved, but fusion and aggregation between the dispersed particles tend to occur, resulting in increased viscosity and poor dispersion, which is unfavorable.

The aqueous polyester resin dispersion of the present invention is preferably produced with a resin solid content concentration of 10 to 45% by mass. More preferably, it is 15-40 mass %, and it is especially preferable that it is the range of 20-35 mass %. When the resin solid content concentration exceeds 45% by mass, the viscosity of the aqueous dispersion becomes high, and aggregation among the resin particles tends to occur, so that the dispersion stability is greatly reduced. Also, if it is less than 10% by mass, it is difficult to say that it is practical in terms of both production and use.

The polyester resin aqueous dispersion of the present invention is most suitable for the inner surface coating of food and beverage cans. In order to make the inner coating of food and beverage cans, various additives are sometimes blended according to the purpose. To the extent that the object of the present invention such as food sanitation and taste is not impaired, a leveling agent for improving coatability, smoothness of the coating film, and appearance, a surfactant, and a substance for preventing damage to the coating film may be blended. Lubricants, which can be blended with colored pigments, polyester resins other than polyester resins (A) and (B) as the case may be, resins other than polyester resins (A) and (B), such as acrylic resin emulsions, polyurethane resins Emulsion etc.

The coating using the polyester resin aqueous dispersion of the present invention can be coated on metal substrates such as aluminum, stainless steel, tinplate, etc. . The film thickness is not particularly limited, and usually the dry film thickness is preferably in the range of 3-18 μm, more preferably in the range of 5-15 μm. The baking conditions of the coating film are usually preferably in the range of about 180-260°C for about 10 minutes to 2 hours, more preferably in the range of about 200-240°C for about 5 minutes-1 hour. [Example]

Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples. The evaluation of various characteristics was carried out according to the following methods. The abbreviation "part" means parts by mass, and the abbreviation "%" means mass %.

＜Polyester resin＞ (1) Determination of resin composition A sample of the polyester resin was dissolved in deuterated chloroform, and 1H-NMR analysis was performed using a nuclear magnetic resonance (NMR) apparatus 400-MR manufactured by VARIAN Corporation. Calculate the molar ratio from the integral value ratio.

(2) Determination of reduced viscosity (unit: dl/g) 0.1 g of a polyester resin sample was dissolved in 25 cc of a mixed solvent of phenol/tetrachloroethane (mass ratio 6/4), and measured at 30°C.

(3) Determination of glass transition temperature (Tg) Measurement was performed with a differential scanning calorimeter (SII company, DSC-200). 5 mg of a sample of the polyester resin was placed in an aluminum stopper-type container, sealed, cooled to -50°C using liquid nitrogen, and then heated up to 150°C at a rate of 20°C/min. In the endothermic curve obtained in this process, the temperature at the intersection of the baseline before the endothermic peak and the tangent to the endothermic peak was taken as the glass transition temperature (Tg, unit: °C).

( ⁴ ) Determination of acid value Dissolve 0.2 g of the sample of polyester resin in 40 ml of chloroform, titrate with 0.01 N potassium hydroxide ethanol solution, and obtain the equivalent (eq/ ton). The indicator is phenolphthalein.

＜Production of polyester resin composition＞ A total of 100 parts by weight (solid content) of polyester resin (A) and polyester resin (B) and catalyst (C) were dissolved in cyclohexanone/Solvesso-150=1/1 (weight ratio), so that This becomes a viscosity suitable for coating. According to the blending in Table 2 and Table 3, a polyester resin composition (solid content about 35% by mass) was obtained.

(5) Determination of THF insoluble matter After heat treatment at 240°C for 5 minutes, the THF insoluble matter is coated with a polyester resin composition on a copper foil so that the thickness after drying becomes 10 μm, and heated at 240°C for 5 minutes to make a length of 10 cm and a width of 2.5 cm. The size of the sample, the mass of the sample before THF immersion is defined as (X), and the mass of the sample after immersing in 60ml of THF at 25°C for 1 hour and drying at 100°C for 10 minutes is defined as the mass after THF immersion (Y ), and obtain it according to the following formula. THF insoluble matter (mass%)={[(Y)-copper foil mass]/[(X)-copper foil mass]}×100 Moreover, the THF insoluble matter after heat-processing at 150 degreeC for 30 minutes was calculated|required similarly to the above except having set the temperature to 150 degreeC and heating for 30 minutes.

＜Preparation of test piece＞ Coat the polyester resin composition on one side of a tin plate (JIS G 3303 (2008) SPTE, 70mm x 150mm x 0.3mm) with a bar coater so that the film thickness after drying becomes 10±2μm, and heat it at 240°C ( PMT: Base material reaches the maximum temperature) × 5 minutes of baking conditions, and hardening baking is performed, and this is used as a test piece (hereinafter referred to as a test piece).

(6) Evaluation of processability The obtained test piece was bent at 180° in the direction in which the cured film was outside, and the cured film cracks generated at the bent portion were measured to evaluate the current flow. In addition, the bending process is performed with nothing interposed therebetween (so-called OT). It is prepared by placing a sponge (width 20mm, depth 50mm, thickness 10mm) impregnated with 1% NaCl aqueous solution on an electrode made of aluminum plate (width 20mm, depth 50mm, thickness 0.5mm), in a way parallel to the 20mm side of the sponge The vicinity of the center of the bent portion of the test piece was brought into contact with the sponge. Apply a DC voltage of 5.0V between the aluminum plate electrode and the non-coated part on the back of the test plate, and measure the conduction value. A smaller energization value means better bending properties. (determination) ◎: Less than 0.5mA ○: More than 0.5mA and less than 1.0mA △: More than 1.0mA and less than 2.0mA ×: 2.0mA or more

(7) Evaluation of curability A gauze felt impregnated with methyl ethyl ketone was pressed against the cured film surface of the test piece so as to be in contact with 1 cm ² , a load of 500 g was applied, and a friction test was performed. The number of times until the cured film peeled off was evaluated according to the following criteria (one reciprocation was defined as one time). (Judgment) ⊚: The coating film did not peel off even after 50 times or more, and no change was observed in the cured film. ○: The cured film peeled off at 25 to 49 times, and the tin plate was exposed. △: The hardened film peeled off at 16 to 24 times, and the tin plate was exposed. ×: The cured film peeled off at 15 times or less, and the tinplate plate was exposed.

(8) Evaluation of retort resistance Put the test piece vertically into a stainless steel cup, inject ion-exchanged water into it until it reaches half the height of the test piece, set it in a pressure cooker of a cooking tester (ES-315 manufactured by Tomy Industries Co., Ltd.), and conduct 125 ℃ × 30 minutes of cooking treatment. The evaluation after treatment was carried out at the steam-contacting part which is expected to be exposed to conditions more severe than those generally used for cured films, and the state of whitening and blistering of the cured film was judged visually as follows. (determination) ◎: Good (no whitening or blistering) ◯: Slight whitening, but no blistering. Δ: There is some whitening and/or some blistering. ×: There is remarkable whitening and/or remarkable blistering.

Synthesis example (a) of polyester resin (A) 740 parts by mass of dimethyl terephthalate, 100 parts by mass of dimethyl 2,6-naphthalene dicarboxylate, 8 parts by mass of trimellitic anhydride, 190 parts by mass of ethylene glycol, and 330 parts by mass of 1,2-propanediol , 190 parts by mass of 1,4-cyclohexanedimethanol, and 0.4 parts by mass of tetra-n-butyl titanate (hereinafter, sometimes abbreviated as TBT) as a catalyst (0.03 mol% relative to the total acid components) were added to 3L In the four-necked flask, the esterification reaction was carried out while gradually raising the temperature to 230° C. over 3 hours. Then, the system was decompressed slowly to 10mmHg over 1 hour to carry out polymerization, and at the same time, the temperature was raised to 250°C, and further, post-polymerization was carried out for 50 minutes under a vacuum of 1mmHg or less. When the target molecular weight was reached, it was cooled to 210°C under nitrogen atmosphere. Then, 26 parts by mass of trimellitic anhydride was added, and stirring was continued for 30 minutes at 200 to 230° C. under a nitrogen atmosphere. This was taken out to obtain the polyester resin of the present invention (synthesis example (a)). The reduced viscosity of the obtained polyester resin was 0.36dl/g, the glass transition temperature (Tg) was 65°C, and the acid value was 300eq/t.

Synthesis example (b)～(k) Using the same direct polymerization method as in Synthesis Example (a), but changing the feed composition, polyester resins of the present invention having resin compositions shown in Table 1 were produced (Synthesis Examples (b) to (k)).

[Table 1] Polyester resin (A) Polyester resin (B) Synthesis example a b c d e f g h i j k Resin composition Carboxylic acid composition (mol%) Terephthalic acid 79 79 78 80 89 79 79 79 78 50 50 2,6-naphthalene dicarboxylic acid 10 10 10 10 10 10 10 10 10 50 50 fumaric acid 10 10 10 10 10 10 10 10 Trimellitic anhydride 1 1 2 1 1 1 1 2 Trimellitic anhydride (post-addition) 3 1 5 3 3 3 3 0.6 6 6 8 Polyol composition (mol%) Ethylene glycol 35 35 35 35 35 50 35 35 56 56 Neopentyl glycol 50 42 42 1,2-propanediol 35 35 35 35 35 70 35 35 1,4-Cyclohexanedimethanol 30 30 30 30 30 30 30 30 Trimethylolpropane 2 2 Resin properties Reduced viscosity (dl/g) 0.36 0.36 0.24 0.36 0.36 0.36 0.36 0.36 0.18 0.18 0.18 Acid value (eq/ton) 300 120 480 300 300 300 300 70 520 600 800 Tg(°C) 65 65 65 65 65 60 90 65 65 55 55

The obtained polyester resin was used to produce a polyester resin composition, and evaluations of processability, curability, and retort resistance were performed. The blending and evaluation results of the polyester resin composition are shown in Table 2 and Table 3.

[Table 2] project Reduced viscosity (dl/g) Acid value (eq/ton) Tg (℃) Example 1 2 3 4 5 6 7 8 9 10 11 12 Polyester resin composition (solid weight ratio) Polyester resin (A) a 0.36 300 65 85 85 70 92 85 85 b 0.36 120 65 85 c 0.24 480 65 85 d 0.36 300 65 85 e 0.36 300 65 85 f 0.36 300 60 85 g 0.36 300 90 85 h 0.36 70 65 Polyester resin (B) i 0.18 520 65 15 15 30 8 j 0.18 600 55 15 k 0.18 800 55 15 15 15 15 15 15 15 Catalyst (C) dodecylbenzenesulfonic acid 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Evaluation THF insoluble matter (mass%) <240°C for 5 minutes> 60 75 80 50 80 85 50 90 65 65 60 60 THF insoluble matter (mass%) <150°C for 30 minutes> 0 0 0 0 0 0 0 0 0 0 0 0 Processability ◎ ◎ ○ ◎ ◎ ◎ ○ ◎ ◎ ◎ ○ ○ sclerosis ◎ ◎ ◎ ○ ◎ ◎ ○ ◎ ○ ○ ○ ○ Retort resistance ○ ◎ ◎ △ ◎ ◎ △ ◎ ○ ○ △ △

[table 3] project Reduced viscosity (dl/g) Acid value (eq/ton) Tg (℃) comparative example 1 2 3 4 5 6 7 8 Polyester resin composition (solid weight ratio) Polyester resin (A) a 0.36 300 65 100 100 30 b 0.36 120 65 100 c 0.24 480 65 100 d 0.36 300 65 e 0.36 300 65 f 0.36 300 60 g 0.36 300 90 100 h 0.36 70 65 85 Polyester resin (B) i 0.18 520 65 100 70 j 0.18 600 55 k 0.18 800 55 15 Catalyst (C) dodecylbenzenesulfonic acid 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Evaluation THF insoluble matter (mass%) <240°C for 5 minutes> 25 40 5 50 30 10 60 70 THF insoluble matter (mass%) <150°C for 30 minutes> 0 0 0 0 0 0 0 0 Processability △ △ x △ x x x x sclerosis △ △ x △ △ x ○ ○ Retort resistance x x x x x x ○ ○

As can be seen from Table 2, the cured film (coating film) obtained from the polyester resin composition using the polyester resin (A) and the polyester resin (B) of the present invention is excellent in processability, curability, and retort resistance. . [industrial availability]

The product of the present invention is a polyester resin composition, an aqueous polyester resin dispersion, and a coating or coating film containing the composition, which are excellent in processability, curability, and retort resistance, and are suitable for coating food and beverages. The main agent of coatings for metal cans, etc.

Claims (11)

A polyester resin composition comprising a polyester resin (A) with an acid value of 100 eq/ton or more and less than 500 eq/ton, and a polyester resin (B) with an acid value of 500 eq/ton or more, wherein the polyester resin ( When the total solid content mass of A) and the polyester resin (B) is 100 parts by mass, the polyester resin (A) is in the range of 55 parts by mass to 95 parts by mass, and the polyester resin (B) is 5 parts by mass or more And the range of 45 parts by mass or less. Such as the polyester resin composition of claim 1, which does not substantially contain a hardener. The polyester resin composition according to claim 1 or 2, wherein the polyester resin (A) contains a diol (a) having two primary hydroxyl groups and does not have an alicyclic structure, and further contains a diol having an alicyclic structure Either or both of (b) and a diol (c) having one primary hydroxyl group and one secondary hydroxyl group and not having an alicyclic structure, as a polyol component constituting the polyester resin (A) . The polyester resin composition according to claim 1 or 2, wherein both the polyester resin (A) and the polyester resin (B) have a branched structure. The polyester resin composition according to claim 1 or 2, wherein the polyester resin (A) contains unsaturated dicarboxylic acid (d) as a polyvalent carboxylic acid component constituting the polyester resin (A). In the polyester resin composition of claim 1 or 2, the tetrahydrofuran insoluble matter after heat treatment at 150°C for 30 minutes is less than 10% by mass, and further contains at least one catalyst (C). The polyester resin composition according to claim 6, wherein the content of the catalyst (C) is 0.01 to 0.5 parts by mass relative to 100 parts by mass of the total amount of the polyester resin (A) and the polyester resin (B). An aqueous polyester resin dispersion, comprising the polyester resin composition according to any one of claims 1 to 7, and an aqueous medium. A coating composition, containing any one of the polyester resin composition according to any one of claims 1 to 7 or the polyester resin aqueous dispersion according to claim 8. A coating film containing the polyester resin composition according to any one of claims 1 to 7. A metal can having the coating film according to claim 10.